Here you have two numbers. Avogadro's number is given with four significant figures, while number 2.0550 is given with five significant figures. That means that your result must be shown with four significant figures. So, 6.022 * 10 ^ 23 / 2.0550 = 2.930 * 10 ^ 23, which has been rounded to four significant figures. Answer: 2.930 * 10 ^ 23
